Keiichi Nagata

Sensor for measuring velocity of vibration using light waveguide

This invention provides a device or method for measuring vibration with high sensitivity and over a wide bandwidth. A curved section is formed in an optical fiber. The curved section is disposed on a place to be measured. Light is input in the optical fiber, and then variation of frequency between the input light and the output light is detected. Infinitesimal vibration applied to the curved section can be measured as variation of frequency between the input light and the output light. Further, it is possible to measure vibration over a wide bandwidth.

CHADS2 and CHA2DS2-VASc scores as bleeding risk indices for patients with atrial fibrillation: the Bleeding with Antithrombotic Therapy Study.

The CHADS2 and CHA2DS2-VASc scores, that is, ischemic stroke risk indices for patients having atrial fibrillation (AF), may also be useful as bleeding risk indices. Japanese patients with AF, who routinely took oral antithrombotic agents were enrolled from a prospective, multicenter study. The CHADS2 and CHA2DS2-VASc scores were assessed based on information at entry. Scores of 0, 1 and ⩾2 were defined as the low, intermediate and high ischemic risk categories, respectively, for each index. Of 1221 patients, 873 took warfarin, 114 took antiplatelet agents and 234 took both. The annual incidence of ischemic stroke was 0.76% in the low-risk category, 1.46% in the intermediate-risk category and 2.90% in the high-risk category by CHADS2 scores, and 1.44, 0.42 and 2.50%, respectively, by CHA2DS2-VASc scores. The annual incidence of major bleeding in each category was 1.52, 2.19 and 2.25% by CHADS2, and 1.44, 1.69 and 2.24% by CHA2DS2-VASc. After multivariate adjustment, the CHADS2 was associated with ischemia (odds ratio 1.76, 95% confidence interval 1.03–3.38 per 1−category increase) and the CHA2DS2-VASc tended to be associated with ischemia (2.18, 0.89–8.43). On the other hand, associations of the indices with bleeding were weak. In conclusion, bleeding risk increased gradually as the CHADS2 and CHA2DS2-VASc scores increased in Japanese antithrombotic users, although the statistical impact was rather weak compared with their predictive power for ischemic stroke.

Development of a new fiber optic vibration sensor and its application to structural health monitoring of composite structures

A new fiber-optic vibration sensor has been developed and applied to structural health monitoring. The sensor is based on new finding that frequency of light wave transmitted through an bended optical fiber is shifted by vibration at the bended region. The principle can be explained that Dopplers effect of the light wave which changes its direction in the optical fiber. Several configurations of the sensor have been designed, and very high sensitivity has been achieved in the extremely wide frequency band by applying laser Doppler velocimetory. Practically numberless sensing points can be arranged on a single optical fiber, and regional monitoring which covers large area of the structures can be achieved. The performance of the sensor is examined experimentally by applying to detection of AE signals and elastic wave propagation in the composite material and adhesive joint test specimens. The experimental results show that the sensitivity is almost equivalent to PZT sensor and that failure of composite materials and debonding in the adhesive joint can be detected successfully. The durable, low-cost and high-sensitive sensor can show a new scope to structural health monitoring in the very variety of applications, for examples, composite aerospace structures, energy plants, piping system, infrastructures such as bridges and tunnels, surface and underground facilities. University and industry collaboration initiated a new business of new NDE for health monitoring and diagnostics.